A current transformer (also known as a series transformer) reduces large voltage currents to smaller values while allowing the user to regulate the electric current via a typical ammeter. In its setup, a primary coil bearing a few coils is connected in series to a current carrying conductor. The secondary winding can be fitted with more coils about a laminated core with a big cross-sectional area.

Conventionally,  either measuring or protective current transformers come in the forms of wound current transformers, toroidal current transformers, and bar current transformers.

Wound current transformers are transformers in which its primary winding is set up in series with the conductor transporting the measured current within the circuit. The size of the secondary current is affected by the number of the transformer’s turns ratio.

Toroidal current transformers are transformers that lack primary winding. The winding carrying the current is fitted through a hole within the toroidal transformer. Certain transformers contain split cores that can be opened, equipped and sealed without interrupting the circuit.

Bar-type current transformers apply cable or bus-bars as primary winding. Entirely insulated from the system’s strong operating voltage, they are normally fastened to the current carrying gadget.